Convectors containing finned tubes are mostly used for heating apartments and buildings. They are designed by taking into consideration the so-called chimney effect. The chimney effect is achieved by meass of an upright channel in which the heating tube provided with fins most of its length. The heating tube raises the temperature of the air in the channel above the temperature of the outer air, and the difference of specific densities of the cold and hot air produces an upright air flow in the channel. The quantity of heat transferred to the air flowing along the finned heating tube depends on the flow velocity, therefore the chimney effect considerably increases the heat released by the heating tube.
The aforesaid chminey effect is usually provided for by means of air-tight walls confining an upright chanel and of a heating tube or several heating tubes arranged at the bottom part of the channel. For aesthetic and hygienic reasons, the upper opening of the channel is closed by means of a grid or a similar element. Such a convector is described in the German published specification No. OS-2 649 770. The drawback of this construction consists in that the bording plates constituting the upright channel do not participate practically in the heat transfer and the grid closing the top of the channel reduces the heating power.
In another known convector flat plates provided with perforations and connected to heating tubes form practically a box. The box is roughly brick-shaped and all of its bording surfaces are provided practically equally with air-permeable perforations. In this solution no air-tightly closed bording surfaces are to be found, consequently the chimney effect is poor. Only a minimum air flow gets through the perforations of the plates so that the surplus effect related to the surplus surface is very low as compared to the above described construction of convector. These heating bodies may be considered rather free-flow radiators than convectors.